The present invention relates to an optical disk device and, for example, can be suitably applied to an optical disk device capable of reproducing a multilayered optical disk.
Conventionally, with optical disks such as DVDs (digital versatile discs) and BDs (Blu-ray Discs), multi-layering of the recording layer has been proposed as means for increasing the recording capacity, and an optical disk with two recording layers has been put into practical use. In order to achieve even greater capacity, it is anticipated that a multilayered optical disk with three or even four or more recording layers will be put into practical use.
As a method of detecting the recording layers in this kind of multilayered optical disk, proposed is a method of using a phenomenon of the amplitude of a focus error signal fluctuating in an S-shape in the vicinity of the recording layer and moving the focal position of the optical beam emitted from the laser diode of the optical disk device in a thickness direction of the multilayered optical disk, and detecting the number of recording layers or the target recording layer based on the number of S-shaped amplitudes (hereinafter referred to as the “S-curve amplitudes”) that are generated in the focus error signal at such time (for example, refer to Japanese Unexamined Patent Application Publication No. 2007-26557).